| The mid-term management,picking and transportation of greenhouse crops are important links in greenhouse production,and the level of mechanization and automation in these links plays a crucial role in greenhouse production efficiency.In view of the mechanization of these operation links,the existing machines are mostly for a specific crop operation links,single function.The multi-functional platform can assist the staff to complete tasks such as forking,tying,fruit picking and transportation of different crops.At present,the operation platform used in greenhouse generally has the problems of poor passability,stability and flexibility,single operation mode and low intelligence degree,which seriously affect the production efficiency in greenhouse.In view of the above problems,this paper designs an electric following operation platform which is suitable for the management,harvesting and transportation of different crops in greenhouse with good passing ability,safety,reliability and high intelligence from miniaturization,mechanization and intelligentization.It can effectively reduce the labor intensity and greatly improve the production efficiency of greenhouse,and has certain significance for the whole mechanization of greenhouse fruit and vegetable productionThis paper mainly conducts research in the following aspects:(1)Comparing various schemes for staff identification,UWB positioning technology is selected as the positioning scheme for staff positioning.A height sensor combined with PDOA algorithm was introduced to realize three-dimensional coordinate positioning of specific personnel,and the positioning error and average value of the algorithm were 12.35 cm.Kalman filter is designed to filter the positioning information,and the positioning accuracy is improved by 56% after filtering.At the same time,in order to reduce the influence of staff posture on the positioning system,the influence of human body posture on the positioning system was studied,and the BP neural network recognition model of the acceleration sensor and staff posture was established,and the recognition accuracy of staff posture was 90%.When the staff turns around 90° and 180°,the positioning accuracy can be improved by 20 cm and 30 cm respectively through the positioning information of human body posture compensation,so as to achieve accurate positioning and improve the stability of the following system when the staff turns around(2)According to the modern greenhouse planting technology and the work requirements of the platform,the crawler chassis,lifting mechanism and platform table are designed.And the platform drive motor,hydraulic system components,drivers,solenoid valves,relays and other hardware selection design.Develop and design the control system with remote control,manual and automatic following functions,design related circuits,and complete the construction of the control system of the operation platform.(3)The differential kinematics model of two wheels of the platform was established to refine the platform following mode.Taking the distance difference between the platform and two ridges as the input of PID controller and the platform wheel speed as the output of PID controller,a linear following strategy based on PID controller was designed and developed to complete the linear following operation between ridges.Secondly,by analyzing the defects of the traditional artificial potential field method,the traditional artificial potential field method was improved in combination with the greenhouse operation environment.The output of the improved artificial potential field method was converted into the velocity and Angle at the next moment of the platform center point,and the velocity of the left and right wheels of the platform was revertically solved according to the kinematics model,so as to complete the platform free following operation.(4)The following platform was tested in the greenhouse.The tests include:minimum turning radius test,slope tilting test,climbing performance test,greenhouse picking and transportation test and following effect test.The test results show that the minimum turning radius of the platform is 1.05 m on average.The slope tilting test shows that under the maximum load of the platform,the tilting angles are 18.2°,12.4°and 10.3°,respectively.According to the results of the platform’s slope tilting test,the platform’s climbing performance test is designed.The results show that the platform can climb through the slope of 15° at different speeds under the maximum load.The experimental results of greenhouse picking and transportation show that the platform can reach the maximum traveling speed of 2km/h,transportation capacity and lifting load of 200 kg,and the maximum lifting height of 1.5m.The following test shows that the average error of the platform’s inter-ridge linear following is 2cm,and the maximum error of the platform’s S-curve path following is 9.74 cm and 3.24 cm,respectively.The maximum values of inter-ridge turn following errors were 4.98 cm and 2.89 cm,respectively.The experimental results show that the platform meets the design requirements in all aspects,and can complete the intelligent operation of greenhouse crop medium-term management,picking and transportation mechanization.This paper developed the greenhouse independent follow multi-functional operation platform,through the study of the greenhouse staff positioning to achieve specific personnel identification and positioning,the development of the following control algorithm,to achieve the platform greenhouse independent follow,reduce the labor intensity of the staff,improve the greenhouse fruit and vegetable medium-term management picking transportation mechanization intelligent level. |
